SELENIUM

Selenium is a non-metallic element that is essential for human health. Approximately 30% of selenium is present in the liver, 30% in muscle, 15% in the kidney, and 10% in the blood plasma. In the body, it is bound to selenium-binding proteins. 

Selenium plays a key role in the immune system functioning and the progression of HIV to AIDS.

Why is Selenium essential for the human body?

• Selenium functions in the human body through seleno-proteins, most of which are oxidant-defense enzymes.
• Other selenium-associated proteins regulate the action of thyroid hormones, Vitamin C, and other molecules.
• Out of the 35 seleno-proteins present in the body, 3 play an active role in thyroid hormone metabolism.  
• Seleno-proteins help to make DNA, protect against cell damage and infections.
• Selenium is a crucial nutrient in HIV-infected patients and ihelps prevent the progression of HIV to AIDS.  
• Selenium is also protective in patients infected with Hepatitis B and Hepatitis C in progressing to malignancy.

What is the recommended daily intake of selenium?

The Recommended Dietary Allowance (RDA) as per the Indian Council of Medical Research (ICMR), is 40 micrograms per day for adults.

What are the signs and symptoms of selenium deficiency?

Selenium deficiency occurs when there is inadequate dietary intake of the mineral, typically due to a scarcity of selenium sources in a given region. A deficiency of this mineral can cause cardiovascular disease, infertility, myodegenerative diseases, and cognitive decline.

Selenium deficiency has been linked mainly to 2 regional diseases: Keshan disease and Kashin Beck’s disease.

– Keshan Disease: It is a disease of the myocardium (the heart muscle). The characteristic sign of this disease is cardiomyopathy. It usually affects children and women of childbearing age in China. In the acute form of this disease, there is a sudden decline in heart function while in chronic Keshan disease, there is heart enlargement. It is important to note that selenium supplements cannot reverse cardiac failure if it has occurred.

– Kashin Beck’s disease: This disease affects growing children in parts of Siberian Russia and China. It is characterized by osteoarthritis involving degeneration and necrosis of the joints and cartilages of legs and arms.

– Suboptimal selenium status may be widespread in the human population. It is accompanied by poor immune functions.

– The early stages of development of the human immune-deficiency virus (HIV) infection are accompanied by a marked decline in plasma selenium. Selenium supplementation in HIV patients has been shown to mark immuno-stimulant effects and, delays/prevents the development of acquired immune deficiency syndrome (AIDS). 

– Selenium has a well-recognized role as an anti-oxidant and anti-inflammatory element. It has proved to be beneficial in inflammatory conditions like rheumatoid arthritis, ulcerative colitis and, pancreatitis.

What are the food sources of Selenium?

Environmental conditions and agricultural practices have a profound influence on the selenium content of many foods. Geographic differences in the content and availability of selenium from the soil to food crops and animal products have a marked effect on the selenium status of entire communities. 

Selenium enters the food chain through plants. The concentration of selenium in plants is directly related to the concentration of the mineral in the soil on which plants were grown.

Plant sources: Whole-wheat, cereals, beans, lentils, brazil nuts.

Animal sources: Eggs, red meat, fish, turkey, beef, chicken, seafood, fortified milk, and milk products.

Can excess selenium lead to toxicity?

There is a very narrow margin between the beneficial and harmful intakes of selenium. Symptoms of chronic selenium toxicity include brittle hair and nails, skin lesions with secondary infections, and garlic odor in the breath. High intake of selenium over a long time, can lead to health problems, ranging from muscle tremors, hair loss, stomach upset, and light-headedness, to more severe outcomes like heart attack, respiratory distress, or kidney failure.

Interesting facts:

• Selenium and iodine share a synergistic relationship that is important for a healthy thyroid. Iodine is a component of thyroid hormone, and selenium (as seleno-protein) helps to convert the thyroid hormone into its active form. Both minerals are needed by the thyroid in adequate amounts; too much of one can contribute to a deficiency of the other.
• Brazil nuts are extremely high in selenium even when grown in low-selenium soil. Eating even one Brazilian nut contains more than the RDA of selenium. Eating too many of these nuts daily can lead to selenium toxicity.